1. Field of the Invention
This invention relates to an apparatus for and method of shaping interconnect leads which have been cut from an interconnect lead tape and have a semiconductor chip attached thereto.
2. Prior Art
In the manufacture of semiconductor packages, a semiconductor chip must be electrically connected to the leads or fingers of a lead frame. In the past, this was accomplished by connecting a relatively small diameter wire between each pad of the semiconductor chip and a respective finger of the lead frame. This interconnect operation is time consuming and relatively expensive. Recently, interconnect lead tapes containing the leads for connecting the semiconductor chip to the fingers of a lead frame have been employed in place of the above-mentioned interconnect wires.
When employing an interconnect lead tape, a semiconductor chip is first attached thereto by bonding the ends of the leads contained on the tape to respective bumps mounted on the pads of the semiconductor chip. Prior to this step in the operation, however, the semiconductor chips on a particular wafer are separated from one another by a saw, but are held in their original position by means of an adhesive backing. After the semiconductor chips are bonded to the ends of the interconnect tape leads, they are pulled off the adhesive backing. Following that step in the operation, the interconnect lead tape, with the semiconductor chips mounted on respective sections thereof, and a lead frame tape are placed in a machine which is capable of cutting out each section of the leads from the interconnect tape and bonding the severed ends thereof to respective fingers of the lead frame. Each section of the interconnect tape which is attached to a semiconductor chip and is to be removed from the remaining portion of the tape during this cutting operation is mounted on a relatively thin film or layer of polyimide which holds the leads together as a unitary article after they are severed.
When a semiconductor chip is removed from the adhesive backing on which it is mounted, the dynamics of the adhesive release control the shape of the interconnect leads to which it is bonded. That is, such pulling forces exerted by the interconnect leads on the semiconductor chip to remove it from its adhesive backing tend to bend the leads and create a basketing effect. However, because of the inconsistencies of the adhesive backing, the basketing effect from one set to another set of interconnect leads will be nonuniform. For example, the thickness of the adhesive may vary, such that different forces are required for separating different chips from the adhesive backing. These release or separation forces which are generated are directly related to the ultimate shape of the interconnect leads. One of the more serious problems which have been encountered is that of having one or more of the interconnect leads bent such that it is brought into contact with the substrate of the semiconductor chip, thereby creating an electrical short therebetween.
One of the solutions which has been considered to solve this problem involves the use of a mechanical probe for mechanically shaping or bending these interconnect leads after the semiconductor chip has been attached thereto. However, such a mechanical probe can create other problems which can be more serious than the problem caused by the uneven bending of the interconnect leads during release of the semiconductor chip attached thereto from its adhesive backing. Such a mechanical probe can cause damage to the semiconductor chip and/or to the interconnect leads. The use of such a mechanical probe involves contacting the chip and/or the ends of the interconnect leads which are attached to the chip and imparting a force thereto while holding the severed ends of the interconnect leads. Such a force must be sufficient to bend the interconnect leads and move the chip with respect to the held ends of the leads. However, such localized forces can cause damage to either the chip and/or the interconnect leads. Furthermore, such localized forces create stresses in the interconnect leads which may result in fracture thereof or in breaking the bond between the lead and a corresponding bump on the chip.
Another problem encountered in the use of a mechanical device to shape such interconnect leads is that of introducing or depositing foriegn matter on the chip and interconnect leads. Such a mechanical device is susceptible of accumulating debris thereon which can be transferred to the chip and the interconnect leads when brought into contact therewith. It has also been found desirable to heat the supportive film on which the interconnect leads are mounted to facilitate shaping thereof. The use of such a mechanical device to shape the leads requires the use of other means for heating the supportive film. Also, such a mechanical device is difficult to control.